11 New Planetary
Systems

NASA's Kepler
Announces 11 New Planetary Systems Hosting 26
Planets

ScienceDaily (Jan. 26, 2012)
— NASA's
Kepler mission has discovered 11 new planetary
systems hosting 26 confirmed planets.
These discoveries nearly double the number of
verified Kepler planets and triple the number of
stars known to have more than one planet that
transits, or passes in front of, the star. Such
systems will help astronomers better understand
how planets form.

The
planets orbit close to their host stars and range
in size from 1.5 times the radius of Earth to
larger than Jupiter. Fifteen are between
Earth and Neptune in size. Further
observations will be required to determine which
are rocky like Earth and which have thick
gaseous atmospheres like Neptune.
The
planets orbit their host star once every six to
143 days. All are closer to their host star than
Venus is to our sun.

"Prior to the Kepler mission, we knew of perhaps
500 exoplanets across the whole sky," said Doug
Hudgins, Kepler program scientist at NASA
Headquarters in Washington. "Now, in just two
years staring at a patch of sky not much bigger
than your fist, Kepler has discovered more than 60
planets and more than 2,300 planet candidates.
This tells
us that our galaxy is positively loaded with
planets of all sizes and orbits."

Kepler identifies planet candidates by repeatedly
measuring the change in brightness of more than
150,000 stars to detect when a planet passes in
front of the star. That passage casts a small
shadow toward Earth and the Kepler spacecraft.

"Confirming that the small decrease in the star's
brightness is due to a planet requires additional
observations and time-consuming analysis," said
Eric Ford, associate professor of astronomy at the
University of Florida and lead author of the paper
confirming Kepler-23 and Kepler-24. "We verified
these planets using new techniques that
dramatically accelerated their discovery."

Each of the newly confirmed planetary systems
contains two to five closely spaced transiting
planets. In tightly packed planetary systems, the
gravitational pull of the planets on each other
causes some planets to accelerate and some to
decelerate along their orbits. The acceleration
causes the orbital period of each planet to
change. Kepler detects this effect by measuring
the changes, or so-called Transit Timing
Variations.

Planetary systems with Transit Timing Variations
can be verified without requiring extensive
ground-based observations, accelerating
confirmation of planet candidates. This detection
technique also increases Kepler's ability to
confirm planetary systems around fainter and more
distant stars.

"By precisely timing when each planet transits its
star, Kepler detected the gravitational tug of the
planets on each other, clinching the case for 10
of the newly announced planetary systems," said
Dan Fabrycky, Hubble Fellow at the University of
California, Santa Cruz, and lead author for a
paper confirming Kepler-29, 30, 31 and 32.

Five of the systems (Kepler-25, Kepler-27,
Kepler-30, Kepler-31 and Kepler-33) contain a pair
of planets where the inner planet orbits the star
twice during each orbit of the outer planet. Four
of the systems (Kepler-23, Kepler-24, Kepler-28
and Kepler-32) contain a pairing where the outer
planet circles the star twice for every three
times the inner planet orbits its star.

"These
configurations help to amplify the gravitational
interactions between the planets, similar
to how my sons kick their legs on a swing at the
right time to go higher," said Jason Steffen, the
Brinson postdoctoral fellow at Fermilab Center for
Particle Astrophysics in Batavia, Ill., and lead
author of a paper confirming Kepler-25, 26, 27 and
28.

Kepler-33,
a star that is older and more massive than our
sun, had the most planets. The system hosts
five planets, ranging in size from 1.5 to 5 times
that of Earth. All of the planets are located
closer to their star than any planet is to our
sun.

The properties of a star provide clues for planet
detection. The decrease in the star's brightness
and duration of a planet transit combined with the
properties of its host star present a recognizable
signature. When astronomers detect planet
candidates that exhibit similar signatures around
the same star, the likelihood of any of these
planet candidates being a false positive is very
low.

"The
approach used to verify the Kepler-33 planets
shows the overall reliability is quite high,"
said Jack Lissauer, planetary scientist at NASA
Ames Research Center at Moffett Field, Calif., and
lead author of the paper on Kepler-33. "This is a
validation by multiplicity."

These discoveries are published in four different
papers in the Astrophysical Journal and the
Monthly Notices of the Royal Astronomical Society.

Ball Aerospace and Technologies Corp. in Boulder,
Colo., developed the Kepler flight system and
supports mission operations with the Laboratory
for Atmospheric and Space Physics at the
University of Colorado in Boulder.